Posted
by
kdawsonon Tuesday June 08, 2010 @07:20PM
from the to-each-its-own dept.

asukasoryu sends along an intriguing piece in light of our recent discussion of possible signs of life on Saturn's moon Titan. "Researchers have discovered that methane-eating bacteria survive in a unique spring located on Axel Heiberg Island in Canada's extreme north. The subzero water is so salty that it doesn't freeze despite the cold, and it has no consumable oxygen in it. There are, however, big bubbles of methane that come to the surface. Lyle Whyte, McGill University microbiologist, explains that the so-called Lost Hammer spring supports microbial life, that the spring is similar to possible past or present springs on Mars, and that therefore they too could support life."

Well, that's the Big Question, isn't it? While it is becoming clear that life can move from an enormously productive biosphere into ecological niches previously thought to be completely inhospitable to life, can it arise in such 'hostile' environments? TFA didn't really go into detail as to the biochemical characterization of the methanogenic critters. Likely that will happen sometime down the line and will be really interesting.

But we're going to have to get our respective asses to Mars if we really want to answer the question.

We are on the verge of having the technology, but no-one seems committed enough. Its as if we are still cave men sitting on the edge of the ocean too afraid to build ourselves a raft even though we've been using rafts for travel along the rivers for as long as the older of us can remember.

Its as if we are still cave men sitting on the edge of the ocean too afraid to build ourselves a raft even though we've been using rafts for travel along the rivers for as long as the older of us can remember.

Good grief, what is it with Slashdot and making analogies that completely miss the point.

Yes, we have built rafts before. However, apart from prestige and long term science the immediate return on investment was rather low. Since at the moment our supplies of food are depleted and the women in the cave

Since at the moment our supplies of food are depleted and the women in the cave are complaining about the children crying all the time because they're hungry, it might not be a bad idea for the cavemen to invest their time hunting for food and postpone the building of the next raft till after the next migration season, when the cave is full of food again.

If you wait until you have no problems before you start investing in the future, you'll never invest, because there will always be problems.

We don't know that. We know that once life gets going it seems to be very resilient and manages to find a lot of different environments to colonize. But we don't know how easy it is for life to start. If life starting is really difficult, then it may be that Titan and Mars are completely barren. What this sort of thing does mean is that if there ever was life on Mars, there's a decent chance that there's still some.

I know it's off-form to re-reply, but sod it, your comment and the one above are too good not to discuss. Yup, you've both hit the nail on the head. I referenced a fictional character (and was also thinking of Stephen Baxter's excellent "Titan") because at the moment SF is at the forefront in many ways. Yes, there may be life out there, but we have exactly as much evidence for it as we do for god (take your pick), exactly none. If there is, then it might be like this, and it's certainly evidence that life, once established, can exist in extreme conditions compared to Earth's "habitable" zones, but until we find life that's without a doubt non-terrestrial then we're a one-off fluke as far as certainties go.

Please mod into oblivion, or re-reply yourselves and be damned with the consequences;)

it strikes me that far from being the sterile lifeless environments that other non-earth planets are assumed to be, that in fact every planet is likely riddled with life in some form, at a microscopic level at the very least. To assume otherwise is perhaps simply subscribing to that eternal 'truth' that humans believe that they are somehow special in the universe. The ancient greeks, as wise as they were, once believed the earth to be at the very centre of things.

It might be difficult to prove that any organisms found elsewhere in the solar system aren't at least distantly related to those on Earth. The solar system being as old as it is, it's entirely possible that over the last three and half billion years or so micro-organisms have traveled between the planets. Deep analysis of their DNA won't necessarily be conclusive, if the organisms were transported between the planetary bodies say three b

On the other hand, if discovery of non-DNA organisms on other planets is followed by detecting similar non-DNA organisms in some niche environment on Earth, we're back to square one with regard to determining the origin of the organisms.

Precisely. Right now we're discovering literally thousands of new organisms a day on our planet as our ability to find them and look deep into what makes them work improves. From what I've been reading recently it looks like we've barely scratched the surfac

Life is not gravity; it is not a force, nor is energy or matter. Life is a description. Life is merely a word we use to describe certain kinds of behavior. Thus, in the same way that orange describes the spectrum of light that we decided we would call orange, we have a perfect* [wikipedia.org] understanding of what constitutes life.

I'm not sure what you meant by your first sentence - I have no personal deities, not even the universe or reality - but the rest of your post is very well said and deserves an insightful moderation.

I have my doubts about whether human beings - or any intelligence that exists within this reality - can ever fully comprehend what they exist within. There are likely hard limits to what an intelligence within a system can learn about that system - of course it may be possible that said intelligen

We learned recently that life can survive in the vacuum and lack of temperature of space. The relevant jump is that life can jump or piggy back on something through like a comet or rock the depths of space. Thus the seed theory (or what ever it's really called)

"I'll go with 'What is Panspermia [wikipedia.org]' for two hundred, Alex?"FTWA:

Hypothesis

The first known mention of the term was in the writings of the 5th century BC Greek philosopher Anaxagoras.[1] In the nineteenth century it was again revived in modern form by several scientists, including Jöns Jacob Berzelius (1834),[2] Kelvin (1871),[3] Hermann von Helmholtz (1879) and, somewhat later, by Svante Arrhenius (1903).Hypothesis

Organisms on Earth which live in extreme environments probably evolved from related species which live in less extreme environments. I have no doubt that there are Terrestrial organisms which could survive in certain environments on Mars, but if they have counterparts on Mars, where did they come from? If they evolved on Mars, there has to have been an environment in which such evolution could have taken place over some kind of condition gradient, from less hostile to more hostile. If they came from Earth, you need a hell of a story about how they got there -- not only are meteor strike ejecta a lot less likely to make it from Earth to Mars than the reverse, you have to envision one piece of rock that just happened to be carrying a viable population of (already rare, even here on Earth) extremophiles that were suited for certain (also very rare) Martian conditions, and landed in just the right place.

If we can ever confirm that Mars had a more life-friendly environment for a significant portion of its history, of course, then these objections can be disregarded. But until we have much more evidence of that than we currently do, I'd be very surprised to find native life on Mars. It's much more likely that if anything is living there, it was carried there by probes from Earth -- and even that seems like a one in a million shot.

About 300kg of rocks make their way from Earth to Mars every year. The reverse is more, about 500kg. The total of "hospitable" rocks that might harbor stowaway life for an Earth to Mars transit is about 150kg/year [tpg.com.au]. So, you see, we're constantly seeding life on Mars.

Interesting link, thanks! And I really hadn't realized that much stuff made it from here to there.

The question is, out of all that, how likely is it that an extremophile suitable for Martian conditions would be one of the passengers, and would land in a hospitable environment on Mars? The link doesn't address that directly, just noting that the Terrestrial organisms would have a good shot if they landed on Mars in a warmer, wetter age -- the problem there being that we don't know if there ever was such a time in Mars' history, or if so, if it lasted long enough to be significant on evolutionary timescales.

Again: extremophiles and the conditions in which they live, are almost by definition rare here on Earth. And conditions suitable for any Terrestrial life are obviously even rarer on Mars, and quite possibly always have been. I'm not saying it's impossible, just that it seems like awfully long odds.

Not very likely, but when we're talking about timescales of billions of years, that changes the odds somewhat;-)

In addition, we *know* that Mars once had enormous oceans of water, probably at a time when the Earth was fairly hospitable to life as well. Given a few hundreds of millions of years of material transfer, it's pretty likely that there was some transference of biologicals, and that some of them found conducive environments on both planets. Remember that many of the extremophiles

The inside of a meteorite is much the same anywhere in the solar system.. that's the point.. the bacteria are bringing their environment with them. The inside of rocks on Mars is much the same as the inside of rocks on Earth, too.

There is a trap in considering average (annual) values because the transfer of rocks occurs in spikes. It is assumed that impacts by asteroids 1km in diameter or larger are needed to launch ejecta into interplanetary flight. Such impacts produce craters 20km or more in diameter. They occur on Mars and Earth (land impacts only) over typical timescales of one to ten million y

There's been an incredible number of papers on the subject, and the overall conclusion is that lithoautotrophic extremophiles most likely do survive the trip. Your objection to the timescales involved is anthropomorphic thinking. On geological timescales the exchange of meteorites between Earth and Mars is constant, and so yes, we are constantly seeding life to Mars.

Well that's the controversial part.. almost every instrument that has been sent to Mars to search for life, actually made it to the surface safely, and managed to turn on, has returned positive results of life on Mars. Every time this has happened there has been denials.. as there's always a malfunction or non-biological explanation that can be used to explain the data. Similarly, every instrument that has returned a negative result for life on Mars (and there's less than have returned positive results) have been shown to be unable to detect life in the extreme locations of Earth, whereas a microbiologist with a $5000 microscope and some plastic slides can find life in these same areas without any trouble. Which is why the question of life on Mars remains open.. and probably will remain open until a sample return mission gives a positive result, and maybe even then not until the first extraterrestrial genome has been sequenced.

As for multi-cellular organisms, for all we know there's plants, moss, or fungi in caves on Mars.. but we'd never know because we've never explored any of them.

That's something that's always bugged me about the Mars missions. Maybe it's just that I've only seen the popular images from the rovers - the panoramas of plains - but it seems fairly obvious to me that if life isn't rampant on Mars then it might be hiding in more sheltered environments, such as caves.

There is the human interest element, too. People see a panorama of Mars and most people say "wow, you went to a lot of trouble to take a photo of some rocks that kinda looks like Arizona through a colour filt

The whole idea of cross contamination across the universe is what makes sense to me. Life in one of the "habitable" planets seeds life in another less "habitable" planet. As that newly arrived "life" thrives, it creates a hospitable environment for other types of organisms which might be arriving on some of the 100 tons of comet debris that enter into the planets atmosphere and/or evolving locally. Effectively the planet changes from a desolate wasteland into a place that can sustain life. Basically the

Glad you asked, cause I love educating random people on Slashdot who can't even be bothered clicking on the links I supply to them, or do their own research.

There's a whole class of bacteria that live inside rocks, they're called lithoautotrophic extremophiles. They suffer through extreme heat and pressures all the time. They have existed for billions of years. When a meteorite impacts the Earth a certain number of these fertile rocks are sent skyward.. the bacteria are protected from the radiation of space by the mass of the rock. Some portion of these rocks are captured by Mars and some even smaller portion are carried to the surface as meteorites. It's a big numbers game.

The speculation is that maybe these extremophiles are now making a living on the Mars service.. bacteria moving from one rock to another isn't that big a stretch of the imagination. Some of them may even make the return trip.

... and the worst is, I do trust that this transfer is valid, and probably along with bacterias, on the million-year average.I would buy this rock-transfer-spawning-life theory for the solar system (while not at all for life coming from elsewhere, in which case the probability just turns so ridiculous it's just a way to refuse thinking about the origins of life).What really turns me sad, is how we can tear true points into pathetically wrong affirmations.I can readily see myself, juste a couple of years fro

All he is saying is that over geological timescales, enough impact events ejecting material out of the atmosphere happen that the resulting debris cloud in space is big enough for a certain mass of material transferred between Earth and Mars per year. Where exactly is it necessary that there is one big impact per year? You think an impact produces straight trajectories of ejected rock from Earth to Mars? There is a shitload of ejected rocks floating around in space, and a certain amount gets captured on a y

Just to clarify for those that did not read the article that you linked:

Ejecta happens very seldom. We are not talking about a constant stream of 300 kgs that constantly goes from Earth to Mars every year, its more like spikes of 3000 tons every 10000 years.
And my guess is, there is a good chance that when a big enough meteor hits earth so an ejecta has good chance to reach Mars, that meteor will wipe all life on earth.

But if you are talking about cosmic time measurements like 1 bilion years, yeah, it

By comparison to Mars, yes, it was. Oh, we wouldn't find it comfortable, of course, but our distant ancestors did -- and there's no evidence that it was "extreme" in the sense that we now talk about such environments. Lots of not-too-briny water (much less salt in the oceans then than now, I'm pretty sure) and a dense atmosphere, even if the composition was very different from the modern one; also temperatures roughly in the range we now consider conducive to life. Except for isolated spots, Mars is just

The problem with making statements about where and what kind of life can exist in the universe is that we have only one data point. That's ignoring the question of what conditions on earth led to life.

The question of what conditions on Earth led to life is impossible to answer (for now). The focus of the article is whether or not life could currently exist on other planets/moons. If it can, it would be worthwhile to make a trip and get a sample. If we have no reason to believe life could exist on Mars or Titan, it would not make sense to go there. There is no problem with questioning the possibility of extraterrestrial life.

The story intrigued me, so I browsed wikipedia searching for the history of the atmosphere and atmospheric methane [wikipedia.org]. I find it very difficult to believe the idea of a chunk of Titan travelling all those years, carrying life and enough reserves of methane for the trip. And since methane used to be much more abundant in the atmosphere, isn't it possible that very old, earthy life forms lived off methane?

That is actually not new research. From geological data it has been clear for a long time that the early atmosphere was reducing, as compared to the oxygen-rich atmosphere we have now, and which is mostly an artifact of life. The earliest atmosphere was probably mostly nitrogen with a mix of CO2, methane and ammonia. That was very early, even before the formation of continents and oceans. With the cooling of the molten Earth, the composition switched to a more water-vapor rich N2/CO2 atmosphere. The true re

When Lovelock was first contracted by NASA to invent machines to search for life, he investigated all sorts of extremophiles--the kind of 'life' we might expect to find on Mars--and quickly concluded that life isn't a bacterium, it is a system of recycling various chemicals that works in conjunction with the sorts of organisms we think of as 'life.' That was his discovery of Gaia. Too many 'real' scientists didn't understand what he had discovered and bought into the greenie definition of Gaia as some sort